A liver assist device (LAD) was developed using cultured cells from differentiated rat liver hepatoma tumors grown to tissue density on multiple artificial capillaries of semipermeable membrane in hollow fiber form. The cells perform metabolic detoxification (bilirubin conjugation with glucuronic acid) and synthetic (coagulation factor synthesis) functions. The LAD placed in an arterio-venous shunt with the rat functioned for the rat by conjugating bilirubin. It is proposed to study several methods for increasing the demonstrated metabolic capacity of the LAD to levels of potential clinical significance by assessing their effect on bilirubin conjugating capacity. The system will be further evaluated in a rat model for fulminant hepatic failure induced by galactosamine hepatotoxicity. To be studied are: 1) the effect of cells with 3-4x increased metabolic capacity for bilirubin conjugation; 2) the effect of using convective trans-capillary membrane mass transfer favoring larger molecules to supplement diffusive transfer used exclusively heretofore, convective transfer to be achieved by alteration of operating flow conditions through the LAD and/or the use of specially constructed novel culture chamber designs as necessary; and 3) the use of larger culture chambers with more and longer capillaries to increase functional cell mass. The resultant metabolic capacity for bilirubin conjugation will be related to human scale liver assist needs and the prospects for scale-up and clinical utility assessed.